Arkell.1956.Jurassic..

NEW CALEDONIA 449
NEW CALEDONIA
The island of New Caledonia, midway between New Guinea and New
Zealand, is 250 miles long by about 40 miles wide. The backbone of the
island is a mountain range which runs longitudinally from end to end, with
many peaks up to about 5000 ft. The range consists mainly of serpentine
and, towards the north and on the north-east side, a mass of metamorphic
rocks, formerly lavas, tuffs and sediments, all believed to be Mesozoic.
On the west side is a coastal belt formed, with adjacent islets, of strongly
folded but unmetamorphosed Mesozoic sediments and volcanic rocks.
The sediments are largely in sublittoral facies and were presumably
formed close to the shore of the Australian continent that lay to the west.
They have been folded and thrust westward during and after intrusion of
the serpentine, which is thought to have arrived as an immense ultrabasic
sill intruded between Middle Eocene and Miocene times. The metamorphic
suite is believed to represent deeper-water equivalents of the
Jurassic and Cretaceous rocks, highly metamorphosed because they lay
above the magma, and were presumably carried westwards on its back.
(Piroutet, 1903, 1917; Benson, 1926a; Jensen, 1936; also Uhlig, 1911,
p. 412, whose brilliant predictions have been confirmed by recent work
by Jensen and Avias.)
The presence of all the stages of the Lower Lias is now established,
chiefly through the work of Avias (1950, 1951, 1954).* Above the Lias
greywackes is a thick carbonaceous formation, consisting predominantly
of black clay-shales, with some lenses of sandstone or arkose, sometimes
containing thin coal seams, and numerous calcareous and siliceous nodules
(Routhier, 1953, p. 49). This formation contains few fossils but is for the
most part Upper Cretaceous, as shown by the presence of Kossmaticeras
spp., which indicate the Senonian. However, in addition three different
Upper Jurassic faunas have been discovered. Flows of andesite and
rhyolite have been reported about the Jurassic-Cretaceous boundary,
and much of the greywacke series contains tuff, as in New Zealand.
The evidence of the faunas may be summarized as follows:—
[BERRIASIAN ?
Sandstones, conglomerates, mudstones and lavas, with gastropods,
especially Dicroloma (Avias, 1954, p. 171, fig. no), and pelecypods which
include Trigoniae close to species in the Umia Beds of Cutch (Piroutet);
but the determinations require confirmation (Routhier, 1953, p. 58).
These beds have also yielded Duvalia and two fragmentary impressions of
Berriasella perhaps comparable with B. novoseelandica (Hochstetter)
(Avias, 1954, pp. 172-3, pi. xx, figs. 13, 14).]
* I am indebted to M. Avias for most kindly sending me advance proofs of his
important monograph (1954), and for supplying the map (fig. 68).
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